Printing and readout system utilizing coding components for symbols,each component having materials which absorb resonantly different gamma rays and cause scattered reradiation,the readout system including a source of different gamma rays corresponding to each of the coding components



A nl 14, 1970 A R. BpHANNAN A 3,505,829

' PRINTING AND READOUT SYSTEM UTILIZING CODING COMPONENTS FOR 4 SYMBOLS EACH COMPONENT HAVING MATERIALS WHICH ABSORB RESONANTLY DIFFERENT GAMMA RAYS AND CAUSE SCATTERED RERADIATION, THE READOUT SYSTEM INCLUDING A SOURCE OF DIFFERENT GAMMA RAYS CORRESPONDING TO EACH OF THE CODING COMPONENTS Filed Feb. 9. 1966 COMPOSITE sfivGLE GAMMA RAY GAMMA RAY -X a DETECTOR A 7+7+m+76 FILTER l 2 TRANSMITTED ?'-RAY.S c0050 FILTER SYMBOL SINGLE GAMMA /4 RAY DETECTOR MULT/ 2/ GAMMA RAY CHANNEL /50URCE GR/VER ANALYZER S/IVGLE GAMMA RAY SOURCE 8 00050 h/SYMBOL 9 7- RAY GAMMA RAY DE TE C TOR GAMMA RAY SOURCE VELOC/ TIES llllll 7 AR 5 6 VELOC/T/ES 0F GAMMA RAY SOURCE J M 3 INTENSITY AT DETECTOR RELATIVE TO CODED SYMBOL INVENTOR ROY BARTON HANNA/V I BY Y A TTORNE Y United States Patent 3,506,829 PRINTING AND READOUT SYSTEM UTILIZING CODING COMPONENTS FOR SYMBOLS, EACH COMPONENT HAVING MATERIALS WHICH AB- SORB RESONANTLY DIFFERENT GAMMA RAYS AND CAUSE SCATTERED RERADIATION, THE READOUT SYSTEM INCLUDING A SOURCE OF DIFFERENT GAMMA RAYS CORRESPONDING TO EACH OF THE CODING COMPONENTS Roy Barton Hannan, Norwalk, Conn., assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine Filed Feb. 9, 1966, Ser. No. 526,179 Int. Cl. G01t 1/16 US. Cl. 25083.3 6 Claims ABSTRACT OF THE DISCLOSURE Coded symbols are formed of inks which have present one or more components of the code in the form of materials which when irradiated with certain bands of recoilless gamma radiation absorb it and reradiate it in all directions. The code may be presence or absence of a component, in which case the number of symbols which can be represented is 2 -1, where n is the number of different components. In order to read out the code the symbol is irradiated with recoilless gamma radiation either with all of the wavelengths to which different components respond or serially with individual ones, and if a particular component is present it absorbs its radiation and reradiates in all directions. Detection can then be obtained by the detector responsive to the particular radiations.

BACKGROUND OF THE INVENTION The problem of coding symbols or messages is becoming of increasing importance and is sometimes loosely referred to as a coding ink system, although symbols do not necessarily have to be formed of fluids which would properly be called inks. In the co-pending application of Freeman and Halverson, Ser. No. 596,366, filed Oct. 14, 1966, and Ser. No. 437,866, filed Mar. 8, 1965, and now abandoned, there is described an information encoding and retrieving system in which inks having diflerent combination of components are used. The components are photoluminescent materials which under ultraviolet light or similar short wave radiation fluoresce in different colors. Ordinary organic fluorescers are often not suitable, at least for the only type of component, because they fluoresce in too broad a band, and therefore in the Freeman and Halverson application it is preferred to have, as at least some if not all of the components, chelated lanthanide ions which under suitable ultraviolet illumination fluoresce in an extremely narrow band. If chelated lanthanide ions are used with one or at most two organic fluorescent compounds, it is possible to prepare inks in which the presence or absence of particular combinations of components constitute the code for a symbol. Basically when using such coded inks, the number of symbols which can be represented are 2 -1, where n is the number of different components. It will be seen that if numbers only are needed, four components are sufficient as this gives the possibility for difierent symbols. However, if letters of the alphabet are also to be included, it is necessary to have six components, which give 63 separate possibilities. With larger numbers of components an even greater number of symbols can be represented.

The Freeman and Halverson application also describes using the components of the coded inks in more than one concentration, that is to say, absent, present in a low See concentration, and present in a much higher concentration, for example ratios of concentrations of 2 to 1. This gives a larger choice, because then the number of symbols is represented by 3 1, which permits symbols with four components. However, this larger number of components is achieved at the loss of sharpness of resolution. If we consider that confusion as to whether a component is present in one level or another as representing a spurious signal, the problem is analogous to signal to noise ratio in electronic circuits, and for convenience this terminology will be used, it being realized of course that the expression is used in a somewhat looser form. When there are only two possibilities, that is to say, presence or absence, a very much higher signal to noise ratio is made possible.

When considering the high signal to noise ratio modification of components which are either present or absent, a problem has arisen with photoluminescent materials because there are only a limited number which are practical. Four can be provided easily, but even six presents a practical problem. The present invention provides multi-component coded inks with a much larger number of components than is readily obtained with photoluminescent components and utilizes a different mechanism for readout. Thus the high signal to noise ratio of coded inks in which components are either present or absent is retained with a possibility of a much larger number of components than is readily practical with photoluminescent materials.

SUMMARY OF THE INVENTION Essentially the present invention utilizes characteristic recoilless gamma radiation from nuclei of diiferent elements or the same element in different environments or both. This is an example using variations of the socalled Mossbauer eifect. This efiect results when the nuslei are present in solid environments, such as different crystals, which influence their characteristic gamma radiation. It should be noted that these characteristic radiations are extremely narrow band. When these gamma rays strike the nuclei and environments of a component of a coded ink which has the same resonant frequency, the radiation is absorbed and re-emitted in random directions.

Two difierent types of readout are possible. In one type a gamma ray source produces the characteristic radiation frequencies of all of the components used in a particular coded ink system. The beam then strikes the symbol to be decoded and if any particular component is present, its

characteristic resonant radiation is absorbed and reemitted in all directions, whereas if the component is absent the radiation passes on through in the same direc tion of the beam. Radiation detectors, one for each component, are arranged outside of the beam so that they en counter only radiations scattered or re-radiated from nuclei of components. The output of these detectors can be used with conventional readout circuitry to produce response according to the symbol of the particular code which is repersented. In general the detectors may be of two different types. In one case they are sensitive only to the extremely narrow band of gamma radiation of a particular component. For example, they may be provided with a window which contains all of the other components, omitting only the particular component the presence of which is to be determined. As a result, each detector will only respond if a particular component is present, and their outputs can be read out by suitable computer circuits of conventional design which will translate the code of the symbols into the symbol desired.

A second type of radiation detector depends on the fact that each narrow band of radiation corresponding to a component will have or can be made to have a somewhat different energy. The detectors respond, substantially nonselectively, to radiations in the bands of any of the components present. However, the response will be different depending on the particular energy, and each detector may be connected to a suitable pulse height deter-mining circuit in a conventional multi-channel analyzer. A fixed response in a band between minimum and maximum may be fixed for each detector output or all of the detector outputs may be successively sampled by a sweep circuit which changes the pulse height response in a repetitive fashion and which then can actuate in suitable time sequence any desired readout mechanism, such as for example a synchronized oscilloscope, multi-channel recorder and the like.

A second principal modification of the present invention involves only a single gamma ray source and a single detector in the line of the beam produced. Now, however, the source is moved, for example oscillated, at various velocities which, by Doppler effect, causes slight displacement in the wavelength or frequency of the radiation. This is the more usual application of the Mtissbauer effect. These dififerent oscillating velocities are synchronized with circuits so that there are sequentially produced signals in which the presence of a particular component is shown by absorption, that is to say by a marked lowering in the signal.

As in the Freeman and Halverson application, the coded inks can be applied either in unshaped forms of symbol or, if it is desired to read the message by visible light, the symbol may be suitably shaped and provided with a pigment or other color which can be seen visibly. This latter form of encoding sacrifices, of course, secrecy, but is desirable for example in the case of account numbers on bank checks where it is frequently desirable to read the account number visually as well as by the gamma ray machine. In every case, one of the big advantages of the coded inks is retained, namely that the symbol is recognized regardless of its shape. which is of practical value since in many cases, of which the bank check account numbers is a typical one, if there is a careless tearing out of the check certain of the symbols may be mutilated. Thus for example an 8 may look like a 9. The present invention shares with the Freeman and Halverson invention the advantages that in such a case the machine readout will give the coded symbol regardless of its shape and so will respond equally to symbols the shape of which may have been inadvertently mutilated.

BRIEF DESCRIPTION OF THE DRAWINGS and single detector using the Mossbauer effect;

FIG. 3 is a curve showing variations of velocity with time, and

FIG. 4 is a graph of current response.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1 the gamma ray source is shown at 7 and is provided with the same number of nuclei, or nuclei and environments, as in the coded ink used, in the illustration six. Six typical components are as follows: Fe 57 in stainless steel. This is considered a reference radiation and the other components differ by energy expressed in terms of mm./ second of source movement to produce the different radiation from the reference by Doppler effect. The other five components are garnet, 0.25 to 0.3; ferrocene, 0.45; FeSn 0.78; ferrous titanate, FeTi O 1.15; and ferrous oxalate, 1.3. The emerging beam from the gamma ray source contains the six different gamma rays as is indicated. This beam strikes the coded item or symbol 8, and any gamma ray frequency which does not correspond to a nucleus present in the coded'symbol passes on in a straight line, as is shown. Where, however, a particular nucleus is present, it scatters the radiation off in all directions.

Around the beam are located six gamma ray detectors, of which 1 and 4 are illustrated on the drawing corresponding to frequencies 7 and Each detector is provided with a filter, filters 11 and 14 being shown; each contains all of the nuclei except the one corresponding to the particular frequency to which the one corresponding to the particular frequency to which the detector is to respond. Thus filter 11 would have the nuclei of compo nents 2 to 6 but would have no component 1 and the filter 14 would have no component 4. The electrical outputs of the gamma ray detectors, which are of conventional design and therefore shown as blocks, are then read out by the conventional electronic circuits, reproducing symbols corresponding to the presence and absence of the particular components. FIGURE 1 would indicate a symbol which had components 1 and 4 but none of the others.

It will be apparent that the response and the readout is unaffected by the shape of the symbol although, as has been pointed out above, if desired the symbol may be shaped and may have a pigment reflecting in the visible so that visual reading can be effected if desired. The coded item 8 is then moved to the next symbol by conventional intermittent moving means (not shown). It will be noted that the modification represented by FIG. 1 has the advantage that there are no moving parts, except of course for the intermittent motion of the symbols, but it suffers from a multiplication of detectors and filters.

If unfiltered detectors are used, as has been described briefly above, a different type of multi-channel analyzer is of course required which may analyze pulse height or other responses resulting from different energies of the different scattered gamma ray bands. The choice of whether to use filtered detectors with relatively simpler readout circuits or unfiltered detectors or detector with more elaborate and sophisticated readout circuits is purely a matter of convenience which will be chosen in accordance with the requirements of a particular use. It is an advantage of the invention that a considerable choice is available so that the best combination for a particular use may be chosen.

FIG. 2 illustrates a second modification utilizing the Mossbauer effect. Here there is a movable gamma ray source 9 which is moved through different discrete velocities by a source driver 10. The motion is indicated on the drawing by the double arrow. FIG. 3 shows a cycle in which. the different velocities v to v are produced successively. The time scale is enoromously exaggerated for clearness as of course the response of detectors is so fast that the duration of any particular velocity can be very short.

After going through the six different velocities, the moving source comes to rest, as is shown on the figure. The coded item which is again shown at 8 intercepts the gamma rays at each different frequency v to v and there is a single detector 20 the output of which goes to a multichannel analyzer 21, the latter being synchronized with source driver 10 so that it switches in channel 1 during the radiation of gamma ray corresponding to velocity v channel 2 corresponding to velocity v etc.

FIG. 4 shows the effect and for simplicity of illustration corresponds to a symbol which contains all six of the components. It will be seen that there is a sharp minimum for each velicity v to v In other words, there will be a minimum signal on all six channels of the multi channel analyzer. If, for example, components 2 and 5 were not present in a particular symbol, there would then be maximum signals on channels corresponding to v and v The output from the multi-channel analyzer is translated into signals in the conventional manner.

In FIGS. 2 to 4, as an example, the moving source can be Fe 57 in a stainless steel matrix, and of course the components of the coded ink would be six different iron compounds each having a diflerent resonance frequency for Fe 57, the resonance frequency corresponding to that produced by the six dilferent velocities of the source. The compounds described in connection with FIG. 1 might be used as one typical example.

The modification of FIGURES 2 to 4 has been described in connection with a single sequence of velocities. Obviously, of course, the sequence of velocities can be repeated at a repetition rate suitable, for example, for the horizontal drive on an oscilloscope or similar readout mechanism. In such a case the symbol would be represented by a curve on the oscilloscope face with minima at the points corresponding to the six different velocities.

Reference has been made to a moving source. Since the Doppler effect is produced by relative movement between source and symbol, it is immaterial Whether the source is moved with a stationary symbol, the symbol moved with a stationary source, or both. For many purposes, such as band checks, movement of the symbol to and from the source presents greater mechanical complicatioss than moving the source. Therefore, in many cases it will be found preferable to move the source only. Of course the symbol is moved intermittently from one symbol to another, but this is motion at right angles to the beam of radiation and has no influence on the Doppler effect.

As the number of various nuclei, wh ch of course includes isotopes, and of crystal environments is very great, no problem is presented with number of components in a coded ink; for example, it is possible to have thirteen different components, which would give a choice of symbols in excess of 8,000. When a very large number of symbols are to be encoded and read out, the second modification shown in FIGS. 2 to 4 presents substantial advantages because there is only a single detector and the cost and spacing of thirteen detectors and filters around the beam, which would be necessary in the modification of FIG. 1, is eliminated. Multi-channel analyzers of course can be built economically with a large number of channels, and so for a large number of components the second modification presents real advantages, It will be apparent that there is a wide flexibiilty in use of the different modifications so that the best one can be chosen with all of the conditions of a particular use in mind. This is a practical advantage of the invention.

I claim:

1. A system for encoding and retrieval of the information in which symbols are encoded with inks having various combinations of presence and absence of a number of nuclei or nuclei and environments having difierent recoilless gamma ray absorption and scattering resonances, which comprises an information retrieving mechanism comprising,

(a) source means for generating a series of gamma rays of frequencies corresponding to the resonance of each of the component nuclei, said means constituting a source,

(b) detection means for detecting radiations corresponding to each of the components of the coded ink,

(c) means for placing the symbols between the gamma ray source and the detection means, and

(d) means for reading out the signals produced by detection to identify the particular symbol.

2. A system according to claim 1 in which the gamma ray radiation source simultaneously emits gamma rays of the frequencies corresponding to the resonances of all of the components of the coded ink and the detection means comprise gamma ray radiation detectors arranged to receive scattered radiation only, each detector producing a signal having a characteristic corresponding to the resonance of a particular component.

3. A system according to claim 2 in which gamma ray detectors corresponding to each component are provided with filters, each filter containing all of the other components of the coded ink except the one which the detector is to detect.

4. A system according to claim "1 comprising a single source of gamma radiation and a single detector, means for interposing a symbol to be detected in a straight line from the radiation source to the detector and means for producing relative motion of the radiation source and the symbols through a series of velocities, each velocity producing by the Doppler eflect a gamma radiation of the frequency corresponding to the absorption of a particular component of the coded ink.

5. A system according to claim 4 in which the source is moved and the symbols remain stationary.

6. A system according to claim 5 in which the output of the single detector is connected to a multi-channel analyzer and means are provided to synchronize the multichannel analyzer with the means for driving the source through the different velocities so that for each particular velocity signals will appear only on a single channel,

presence of a component being indicated by minimum signal.

References Cited UNITED STATES PATENTS 3,193,683 7/1965 Reiifel 250-83 X 3,257,558 6/1966 Cook et al 250-833 RALPH G. NILSON, Primary Examiner A. B. CROFT, Assistant Examiner U.S. Cl. X.R. 25084, 106 

